Repository logo

Browsing by Author "Kuznetsov, Maxim L."

Now showing 1 - 2 of 2
  • Interaction of [(VO)-O-IV(acac)(2)] with Human Serum Transferrin and Albumin
    Publication . Correia, Isabel; Chorna, Ielyzaveta; Cavaco, Isabel; Roy, Somnath; Kuznetsov, Maxim L.; Ribeiro, Nadia; Justino, Goncalo; Marques, Fernanda; Santos-Silva, Teresa; Santos, Marino F. A.; Hugo, M. Santos E.; Capelo, Jose L.; Doutch, James; Pessoa, Joao Costa
    VO(acac)(2)] is a remarkable vanadium compound and has potential as a therapeutic drug. It is important to clarify how it is transported in blood, but the reports addressing its binding to serum proteins have been contradictory. We use several spectroscopic and mass spectrometric techniques (ESI and MALDI-TOF), small-angle X-ray scattering and size exclusion chromatography (SEC) to characterize solutions containing [VO(acac)(2)] and either human serum apotransferrin (apoHTF) or albumin (HSA). DFT and modeling protein calculations are carried out to disclose the type of binding to apoHTF. The measured circular dichroism spectra, SEC and MALDI-TOF data clearly prove that at least two VOacac moieties may bind to apoHTF, most probably forming [(VO)-O-IV(acac)(apoHTF)] complexes with residues of the HTF binding sites. No indication of binding of [VO(acac)(2)] to HSA is obtained. We conclude that (VO)-O-IV-acac species may be transported in blood by transferrin. At very low complex concentrations speciation calculations suggest that [(VO)(apoHTF)] species form.
    2017-08Journal article Open access Show more
  • Organocatalyzed oxidation of benzyl alcohols by a tetrazole-amino-saccharin: A combined experimental and theoretical (DFT) study
    Publication . Frija, Luis M. T.; Kuznetsov, Maxim L.; Rocha, Bruno G. M.; Cabral, Lília; Cristiano, Maria Lurdes Santos; Kopylovich, Maximilian N.; Pombeiro, Armando J. L.
    A new catalytic system for the anaerobic oxidation of benzyl alcohols using a tetrazole-amino-saccharin organocatalyst has been established. In a solvent-free and microwave assisted process comprising aqueous tert-butyl hydroperoxide (TBHP) as oxidant, a variety of benzyl alcohols has been efficiently converted to aldehydes under mild conditions. Most reactions are complete within 30 min and the catalyst exhibits varied functional group compatibility. A catalytic cycle for the oxidation of the alcohols promoted by the tetrazole-amino-saccharin derivative is outlined involving radical species. DFT calculations performed for the oxidation of benzyl alcohol with and without organocatalyst show that the rate limiting step of the whole reaction is the cleavage of the O-O bond in TBHP with the subsequent hydrogen abstraction from the alcohol. The tetrazole-amino-saccharin organocatalyst assists the H-abstraction from benzyl alcohol by the bound HO center dot radical. The simplicity, selectivity and softness of reaction conditions of the studied organocatalytic protocol suggest a great potential for extensive use in synthetic chemistry. (C) 2017 Elsevier B.V. All rights reserved.
    2017-12Journal article Restricted access Show more